The exhaust gases generated by internal combustion engines such as found in vehicles are exhausted through an exhaust system. The typical exhaust system includes a relatively small diameter pipe extending from the exhaust manifold to an opening to the atmosphere with one or more muffler sections along the pipe. The typical muffler is a heavy, bulky device of much larger diameter than the remainder of the system.
The muffler is employed to break down within a relatively short distance the sonic shock waves generated by the explosive release of the combusted air/fuel mixture from the cylinders. The shock waves include sound waves of various frequencies. The muffler is designed to break up the sound waves of various frequencies by structure well understood in the art.
The large size of the muffler results in a greater likelihood of road damage and imposes space limitations which must be designed for in the vehicle. When the exhaust system cools, the large, confined space within the muffler condenses moisture, which contributes to rusting and deterioration of the muffler. A muffler is relatively complex in construction and requires several different pieces of metal to be processed in different techniques. The muffler is therefore relatively expensive and heavy.
In recent years, the exhaust system has also been required to eliminate unburned hydrocarbons from the exhaust gases. This function has been performed by a separate catalytic converter. The converter is essentially an add on to the conventional exhaust system and again forms a relatively bulky container. The exhaust gases with unburned hydrocarbons flow into the converter and are passed over catalysts from the precious metals of the platinum group, including platinum, palladium and rhodium, all plated over alumina. The alumina can be in pellet form or carried on a substrate of extruded ceramics. The converter acts to oxidize the hydrocarbons to reduce the pollutants in the atmosphere. Again, the converter's bulk requires the design of the vehicle to be specially adapted to accept the converter. The oxidation of the unburned hydrocarbons generates a great deal of heat and the converter reaches a high temperature. The vehicle must also be designed to insure no damage results from this high temperature.
The conventional muffler, converter, interconnecting pipe, exhaust pipe and tail pipe are connected by clamps and mounted on the vehicle through mounting brackets. The various components must be assembled and positioned on the vehicle on the assembly line. The relative complexity of the design results in a lengthy and costly assembly operation.
A need exists for an improved exhaust system which retains the muffling and oxidation features of the conventional muffler and converter with reduction of the size, cost and weight of the system. This would increase the flexibility of vehicle design. There is also a need to develop an improved exhaust system which reduces assembly time and material cost with equivalent or improved durability during use. A recent attempt to achieve some of these goals is the device in U.S. Pat. No. 3,746,126 issued July 17, 1973 to de Cardenas.